(a) For purposes of determining a transferring member's eligibility for retirement in accordance with section twenty-five, article seven-a of this chapter, any member who has affirmatively elected to transfer to the state Teachers Retirement System pursuant to the provisions of this article shall be fully credited for his or her years of service in the Teachers' Defined Contribution Retirement System: Provided, That the calculation of any transferring member's service credit in the state Teachers' Retirement System following the transfer shall be determined in accordance with the provisions of section six of this article.

(b) For purposes of this section, "years of service" shall mean all years as a member of the Teachers' Defined Contribution Retirement System and, in addition thereto, credits for any prior service, if any: Provided, That service previously withdrawn by a member may not be included in "years of service" unless repaid.